A firestop is a device that impedes the passage of smoke and flames through a wall or floor adjacent a pipe, conduit, duct, electrical cable or other structure. Building codes for commercial and residential structures often require the installation of a firestop capable of containing fire and smoke for a certain period of time. For example, FIG. 1 illustrates a pipe 10 that passes through wall 12 and floor 14 at locations A and B, respectively. If no firestop is provided, smoke and flames emanating from burning object 16 may pass into adjacent rooms through the gap between pipe 10 and wall 12 or floor 14.
Additionally, a pipe may move radially, axially, or both relative to the partition through which it extends due to thermal expansion and contraction, shifting of the structure, seismic activity, and other factors. Repeated movement of the pipe relative to the partition may compromise the integrity of a conventional firestop. For example, a pipe has a certain equilibrium length at room temperature. If heated water is forced through the pipe (such as water from a boiler), the pipe will tend to expand both longitudinally and radially. When the pipe is cooled, it will tend to return to its equilibrium length. For example, a 30.5 meter (100.0 ft) section of cast iron pipe may expand 27.2 mm (1.1 inches) if heated from an ambient temperature of 42.2.degree. C. (60.degree. F.) to 202.degree. C. (220.degree. F.). A similar length of copper pipe may expand 44.7 mm (1.76 inches). In a fire, temperatures may reach 927.degree. C. (1700.degree. F.) resulting in linear expansion of 276.9 mm (10.9 inches) for a 30.5 meter (100.0 ft) section of cast iron pipe and 457.2 mm (18.0 inches) for copper pipe. If the pipe has an elbow, such as the pipe shown in FIG. 1, the pipe may undergo longitudinal expansion in two directions, labelled D1 and D2 in FIG. 1. Thus, it is desirable for a firestop to permit repeated axial and radial movement of a pipe due to thermal expansion, for example, without degrading the structural integrity of the fire stop.
One known firestop includes caulk, putty, or the like packed around the perimeter of the pipe at the junction between the pipe and the partition. Such a firestop may have utility from the standpoint of impeding the passage of smoke, but may not be suitable for environments in which the pipe moves substantially relative to the partition, due in part to different thermal expansion coefficients for the pipe, the caulk, and the wall. Furthermore, the caulk may dry and crack over time, thereby losing effectiveness as a firestop. Most importantly, the caulk typically can accommodate pipe movement of less than 12 mm (0.5 inches). Consequently, the caulk may become separated from the pipe or the partition or both after a sufficient number of expansion and contraction cycles, compromising the effectiveness of the firestop.
Another known firestop is illustrated in FIG. 2, wherein pipe 10' passes through wall 12'. The firestop 20 may be applied on one or both sides of wall 12', and generally includes a flexible boot 22 circumferentially attached to pipe 10' by band clamp 24. The other end of flexible boot 22 is attached to wall 12' by wall ring 26. Flexible boot 22 is typically provided with a fire-proof or fire-resistant layer 28 facing pipe 10', to shield pipe 10' from fire near the opening in wall 12'. Fire-proof layer 28 may comprise such materials as fiberglass or a mat constructed of ceramic insulation materials.
While having its own utility, the firestop illustrated in FIG. 2 may exhibit certain disadvantages. For example, the fire-proof layer 28 may tend to deteriorate after many expansion and contraction cycles. Similarly, the flexible boot may also deteriorate after many expansion and contraction cycles, which could compromise the effectiveness of the firestop. Moreover, depending on the characteristics of the particular firestop, the flexible boot 22 may not have the capacity to accommodate extreme movement of the pipe 10' due to extreme thermal expansion of the pipe during a fire.
It is therefore desirable to provide a firestop that accommodates movement of pipe with respect to a partition that remains effective after many expansion and contraction cycles.